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Abstract:

The vehicle crew communication system provides up to sixty wireless
headsets that can be used with one base station, a range of 1600 feet
from the base station for operation of the headsets, full duplex
operation communication over digitally encrypted DECT protocol links from
one base station to a plurality of headsets, pairing of each headset to a
particular base station, use of wireless technology inside and outside of
the vehicle, automatic channel and link selection to transparently avoid
interfered-with channels and links, removal of the need to manually
select a channel on the headset, and the combination of the
noise-cancelling microphone with noise threshold, noise attenuation, and
line echo cancellation tuned to intercom parameters. The invention may be
used with or without a vehicle.

Claims:

1. A vehicle crew communications system comprising: a. at least one base
station having a first plurality of channels, wherein each channel of
said plurality of channels comprises a second plurality of slots; b. an
intercom communicatively coupled to said at least one base station via a
microphone input in said intercom; c. at least one wireless headset
wirelessly communicatively coupled via a wireless TDMA link to a
particular one base station of said at least one base station; d. wherein
the system further comprises: i. a plurality of wireless headsets, of
said at least one wireless headset, concurrently usable with one base
station of said at least one base station; ii. full duplex communication
over digitally encrypted DECT protocol links from one said base station;
and iii. automatic selection of said slot and said channel to avoid
interference, wherein said selection is transparent to said users.

2. The vehicle crew communications system of claim 1, further comprising
at least one radio communicatively coupled to said intercom.

3. The vehicle crew communications system of claim 1, further comprising
a range of up to and including sixteen hundred feet over which said at
least one wireless headset is operable.

4. The vehicle crew communications system of claim 1, further comprising
a range of up to and including twenty-eight hundred feet over which said
at least one wireless headset is operable.

5. The vehicle crew communications system of claim 1, further comprising
pairing of each particular headset of said at least one wireless headset
to a particular base station of said at least one base station.

6. The vehicle crew communications system of claim 1, further comprising
a noise-cancelling microphone with noise threshold, noise attenuation,
and line echo cancellation tuned to parameters of said intercom.

7. The vehicle crew communications system of claim 1, further comprising
non-manual selection of said channel for said at least one wireless
headset.

8. The vehicle crew communications system of claim 1, wherein said
plurality of headsets comprises up to sixty headsets concurrently usable
with one base station of said at least one base station.

9. The vehicle crew communications system of claim 1, wherein said
plurality of headsets comprises up to one hundred twenty headsets
concurrently usable with one base station of said at least one base
station.

10. The vehicle crew communications system of claim 1, wherein said at
least one base station comprises five or less base stations.

11. The vehicle crew communications system of claim 10, wherein said at
least one wireless headset comprises four or less said wireless headsets
per base station.

12. The vehicle crew communications system of claim 1, wherein each base
station of said at least one base station provides at least five channels
each having: a. twelve full-duplex TDMA links; b. a DECT protocol in the
1920-1930 GHz sub-band; c. a firmware digital signal processing algorithm
for reducing line echo; and d. encryption.

13. The vehicle crew communications system of claim 1, wherein each base
station of said at least one base station provides at least ten channels
each having: a. twelve full-duplex TDMA links; b. a DECT protocol in the
1880-1900 GHz sub-band; c. a firmware digital signal processing algorithm
for reducing line echo; and d. encryption.

14. The vehicle crew communications system of claim 1, wherein a
particular said wireless headset of said at least one wireless headset
comprises: a. a head-engaging web; b. a noise-canceling microphone
coupled to said web; c. a microphone circuit coupled to said microphone,
wherein said microphone circuit employs noise-gating; d. noise-reduction
ear covers coupled to said web; e. a volume control switch; and f. a
push-to-talk (PTT) switch.

15. The vehicle crew communications system of claim 14, wherein said
microphone is automatically constantly on and said PTT switch provides
access to said at least one radio when said PTT switch is activated.

16. The vehicle crew communications system of claim 14, wherein said
microphone is not automatically constantly on and said PTT is operable to
switch said microphone to constantly on.

17. The vehicle crew communications system of claim 14, wherein said
microphone is never constantly on and said PTT switch comprises an
off-biased button PTT switch operable to turn on said microphone only
while said off-biased button PTT switch is depressed.

18. The vehicle crew communications system of claim 14, wherein said
microphone circuit employs noise gating tuned to said microphone input of
said intercom and further provides balancing of an audio level to allow
the user's voice to break over said noise gate.

19. The vehicle crew communications system of claim 1, wherein said base
station comprises firmware comprising an adaptive digital signal
processing algorithm to reduce side tone from said at least one wireless
headset.

20. The vehicle crew communications system of claim 1, wherein said at
least one wireless headset comprises at least one rechargeable headset
battery, the system further comprising a battery charger for charging
said at least one rechargeable battery.

21. The vehicle crew communications system of claim 1, wherein said at
least one wireless headset comprises at least one rechargeable headset,
the system further comprising a charger for charging said at least one
rechargeable headset.

22. A vehicle crew communications system comprising: a. at least one base
station; b. an intercom communicatively coupled to said at least one base
station via a microphone input in said intercom and also communicatively
coupled to at least one radio; c. at least one wireless headset
wirelessly communicatively coupled via a TDMA link to a particular one
base station of said at least one base station; d. wherein the system
further comprises: i. one of: 1. up to sixty headsets of said at least
one wireless headset usable at once with one base station of said at
least one base station; and 2. up to one hundred twenty headsets of said
at least one wireless headset usable at once with one base station of
said at least one base station; ii. one of: 1. a range of up to sixteen
hundred feet from said at least one base station over which said at least
one wireless headset is operable; and 2. a range of up to twenty eight
hundred feet from said at least one base station over which said at least
one wireless headset is operable, respectively; iii. full duplex
communication over digitally encrypted DECT 6.0 protocol links from one
said base station; iv. pairing of each particular headset of said at
least one wireless headset to a particular base station of said at least
one base station; v. automatic link and channel selection to avoid
interference, wherein said selection is transparent to said users; i.
non-manual selection of a channel for said at least one wireless headset;
and ii. a noise-cancelling microphone with noise threshold, noise
attenuation, and line echo cancellation tuned to parameters of said
intercom.

23. The vehicle crew communications system of claim 22, wherein said at
least one base station comprises five or less base stations.

24. The vehicle crew communications system of claim 23, wherein said at
least one wireless headset comprises four or less said wireless headsets.

25. The vehicle crew communications system of claim 22, wherein
microphone is automatically constantly on and said PTT switch provides
access to said at least one radio when said PTT switch is activated.

26. The vehicle crew communications system of claim 22, wherein each base
station of said at least one base station provides at least ten channels
each having: a. twelve full-duplex TDMA links; b. a DECT protocol in the
1880-1900 GHz sub-band; c. a firmware digital signal processing algorithm
for reducing line echo; and d. encryption.

27. The vehicle crew communications system of claim 22, wherein each base
station of said at least one base station provides five channels each
having: a. twelve full-duplex TDMA links; b. a DECT protocol in the
1920-1930 GHz sub-band; c. a firmware digital signal processing algorithm
for reducing line echo; and d. encryption.

28. The vehicle crew communications system of claim 22, wherein a
particular said wireless headset of said at least one wireless headset
comprises: a. a noise-cancelling microphone; b. a microphone circuit
coupled to said microphone, wherein said microphone circuit employs noise
gating tuned to said microphone input of said intercom and further
provides balancing of an audio level to allow the user's voice to break
over said noise gate; c. noise reduction ear covers; d. a volume control
switch; and e. a push-to-talk (PTT) switch.

29. The vehicle crew communications system of claim 22, wherein said at
least one wireless headset comprises at least one rechargeable headset
battery, the system further comprising a battery charger for charging
said at least one rechargeable headset battery.

30. The vehicle crew communications system of claim 22, wherein said base
station comprises firmware comprising an adaptive digital signal
processing algorithm to reduce side tone from said at least one wireless
headset.

31. A vehicle crew communications system comprising: a. a plurality of
base stations wherein: i. each base station of said plurality of base
stations provides at least one of: 1. five channels each having: a.
twelve full-duplex TDMA links; b. a DECT protocol in the 1920-1930 GHz
sub-band; c. an adaptive DSP algorithm incorporated in firmware for
attenuating side tones; and d. encryption; and 2. ten channels each
having: a. twelve full-duplex TDMA links; b. a DECT protocol in the
1880-1900 GHz sub-band; c. an adaptive DSP algorithm incorporated in
firmware for attenuating side tones; and d. encryption; and ii. said
plurality of base stations comprises no more than five base stations; b.
an intercom communicatively coupled to: i. at least one base station of
said plurality of base stations via a microphone input in said intercom,
wherein: 1. audio levels from said intercom to said base station are
frequency and gain matched to said base station; and 2. audio levels from
said base station to said intercom are frequency and gain matched to said
intercom; and ii. at least one radio; c. four or fewer wireless headsets
each wirelessly communicatively coupled via respective TDMA links to
particular respective base stations of said plurality of base stations,
wherein each said wireless headset comprises: i. a head-engaging web; ii.
a noise-cancelling microphone coupled to said web; iii. a microphone
circuit coupled to said microphone; iv. a pair of noise-reduction ear
covers coupled to said web; v. a volume control switch coupled to one
noise-reduction ear cover of said pair of said noise-reduction ear
covers; vi. a push-to-talk (PTT) switch coupled to one noise-reduction
ear cover of said pair of said noise-reduction ear covers, wherein said
PPT switch is operable to at least one of: 1. access said radio; 2.
switch said microphone from off to continuously on; and 3. switch said
microphone from off to momentarily on; and d. further comprising: i. one
of 1. up to sixty wireless headsets of said at least one wireless headset
usable at once with one base station of said at least one base station;
and 2. up to one hundred twenty wireless headsets of said at least one
wireless headset usable at once with one base station of said at least
one base station; and ii. a range that is one of: 1. up to sixteen
hundred feet over which said at least one wireless headset is operable;
and 2. up to twenty eight hundred feet over which said at least one
wireless headset is operable, respectively; iii. full duplex
communication over digitally encrypted DECT protocol links from each said
base station of said plurality of base stations; iv. pairing of each
particular wireless headset of said at least one wireless headset to a
particular base station of said plurality of base stations; v. automatic
link and channel selection to avoid interference, wherein said selection
is transparent to said users; vi. non-manual selection of a channel for
said at least one wireless headset; and vii. a noise-cancelling
microphone with noise threshold, noise attenuation, and line echo
cancellation tuned to parameters of said intercom.

Description:

RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of pending
U.S. application Ser. No. 12/567,377 filed Sep. 25, 2009 to the same
inventors which, in turn, claims the benefit of U.S. provisional
application 61/099,982 filed Sep. 25, 2008 by the same inventors.

FIELD OF THE INVENTION

[0002] The present invention generally relates to a system for providing
wireless communications, preferably between members of a vehicle crew,
both inside the vehicle and outside the vehicle within a broad
operational range (up to 1600 feet in US, 2800 feet outside US) of a base
station, preferably on a particular point on the vehicle. Particular
embodiments of the invention relate to emergency response vehicles, such
as fire trucks and ambulances, but other vehicles and even fixed
installations may use the system.

BACKGROUND OF THE INVENTION

[0003] Wired intercoms for communicating between crew members of vehicles
are well known. U.S. Pat. No. 6,223,062 B1 for a COMMUNICATIONS INTERFACE
ADAPTER issued to Davidson et al. on Apr. 24, 2001, discloses an
interface between a vehicle intercom and a radio transceiver that allows
a crew member who has disconnected from the wired intercom to access the
wired intercom from outside the vehicle via radio transceiver through the
communications interface adapter to the intercom.

[0005] Accordingly, it is desirable to provide an vehicle crew
communication system that is entirely wireless, resistant to
interference, allows a plurality of disembarked crew members to
communicate over the intercom at operationally useful distances, allows
wireless communication within the vehicle, and avoids aggregating
adapters to legacy systems. It is further desirable to have a vehicle
crew communication system that permits intercom headset access to one or
more radios for longer range communications.

BRIEF SUMMARY OF THE INVENTION

[0006] A system is provided for providing interference-resistant wireless
communications for a vehicle crew both embarked in and disembarked from
the vehicle, and for other purposes. The system provides a five-channel
base station (corresponding to five allocated channels in the 1.90-1.92
GHz band) able to communicate with up to sixty headsets by virtue of the
twelve TDMA full-duplex slots in each channel. The bandwidth is
sufficient to allow for digital encryption, thereby reducing the
likelihood of interception during use in national security applications.
Channel selection is performed automatically, using the DECT 6.0 protocol
(or follow-on) in the US or DECT in Europe, so hand selection of
channels, and errors made in that process, are avoided. Likewise,
resistance to interference is enhanced by the use of DECT 6.0 (or
follow-on) and DECT protocols. The combination of the communications
system and the vehicle is within the scope of the invention, as well as
the communications system alone. Outside the US, base stations may have
ten base stations in the 1880-1900 GHz band allowing for use of up to 120
wireless headsets per base station.

[0007] A vehicle crew communications system including: a base station
having a first plurality of channels, where each channel of the plurality
of channels includes a second plurality of slots; an intercom
communicatively coupled to the base station via a microphone input in the
intercom; a wireless headset wirelessly communicatively coupled via a
wireless TDMA link to a particular one base station; where the system
further includes: a plurality of the wireless headsets concurrently
usable with one base station; full duplex communication over digitally
encrypted DECT protocol links from the base station; and automatic
selection of the slot and the channel to avoid interference, where the
selection is transparent to the users. The vehicle crew communications
system, further including a radio communicatively coupled to the
intercom. The vehicle crew communications system, further including a
range of up to and including sixteen hundred feet over which the wireless
headset is operable. The vehicle crew communications system, further
including a range of up to and including twenty-eight hundred feet over
which the wireless headset is operable. The vehicle crew communications
system, further including pairing of each particular headset to a
particular base station. The vehicle crew communications system, further
including a noise-cancelling microphone with noise threshold, noise
attenuation, and line echo cancellation tuned to parameters of the
intercom. The vehicle crew communications system, further including
non-manual selection of the channel for the wireless headset. The vehicle
crew communications system, where the plurality of headsets includes up
to sixty headsets concurrently usable with one base station of the base
station. The vehicle crew communications system, where the plurality of
headsets includes up to one hundred twenty headsets concurrently usable
with one base station of the base station. The vehicle crew
communications system, where the base station includes five or less base
stations. The vehicle crew communications system, where the wireless
headset includes four or less wireless headsets per base station. The
vehicle crew communications system, where each base station provides at
least five channels each having: twelve full-duplex TDMA links; a DECT
protocol in the 1920-1930 GHz sub-band; a firmware digital signal
processing algorithm for reducing line echo; and encryption. The vehicle
crew communications system, where each base station of the base station
provides at least ten channels each having: twelve full-duplex TDMA
links; a DECT protocol in the 1880-1900 GHz sub-band; a firmware digital
signal processing algorithm for reducing line echo; and encryption. The
vehicle crew communications system, where a particular wireless headset
includes: a head-engaging web; a noise-canceling microphone coupled to
the web; a microphone circuit coupled to the microphone, where the
microphone circuit employs noise-gating; noise-reduction ear covers
coupled to the web; a volume control switch; and a push-to-talk (PTT)
switch. The vehicle crew communications system, where microphone is
automatically constantly on and the PTT switch provides access to the
radio when the PTT switch is activated. The vehicle crew communications
system, where the microphone is not automatically constantly on and the
PTT is operable to switch the microphone to constantly on. The vehicle
crew communications system, where the microphone is never constantly on
and the PTT switch includes an off-biased button PTT switch operable to
turn on the microphone only while the off-biased button PTT switch is
depressed. The vehicle crew communications system, where the microphone
circuit employs noise gating tuned to the microphone input of the
intercom and further provides balancing of an audio level to allow the
user's voice to break over the noise gate. The vehicle crew
communications system, where the base station includes firmware including
an adaptive digital signal processing algorithm to reduce side tone from
the wireless headset. The vehicle crew communications system, where the
wireless headset includes a rechargeable headset battery, the system
further including a battery charger for charging the rechargeable
battery. The vehicle crew communications system, where the wireless
headset includes a rechargeable headset, the system further including a
charger for charging the rechargeable headset.

[0008] A vehicle crew communications system including: a base station; an
intercom communicatively coupled to the base station via a microphone
input in the intercom and also communicatively coupled to a radio; a
wireless headset wirelessly communicatively coupled via a TDMA link to a
particular base station; where the system further includes: one of: up to
sixty headsets of the wireless headset usable at once with one base
station of the base station; and up to one hundred twenty headsets of the
wireless headset usable at once with one base station of the base
station; one of: a range of up to sixteen hundred feet from the base
station over which the wireless headset is operable; and a range of up to
twenty eight hundred feet from the base station over which the wireless
headset is operable, respectively; full duplex communication over
digitally encrypted DECT 6.0 protocol links from the base station;
pairing of each particular headset of the wireless headset to a
particular base station; automatic link and channel selection to avoid
interference, where the selection is transparent to the users; non-manual
selection of a channel for the wireless headset; and a noise-cancelling
microphone with noise threshold, noise attenuation, and line echo
cancellation tuned to parameters of the intercom. The vehicle crew
communications system, where the base station includes five or less base
stations. The vehicle crew communications system, where the wireless
headset includes four or less the wireless headsets. The vehicle crew
communications system, where microphone is automatically constantly on
and the PTT switch provides access to the radio when the PTT switch is
activated. The vehicle crew communications system, where each base
station provides at least ten channels each having: twelve full-duplex
TDMA links; a DECT protocol in the 1880-1900 GHz sub-band; a firmware
digital signal processing algorithm for reducing line echo; and
encryption. The vehicle crew communications system, where each base
station provides five channels each having: twelve full-duplex TDMA
links; a DECT protocol in the 1920-1930 GHz sub-band; a firmware digital
signal processing algorithm for reducing line echo; and encryption. The
vehicle crew communications system, where a particular wireless headset
includes: a noise-cancelling microphone; a microphone circuit coupled to
the microphone, where the microphone circuit employs noise gating tuned
to the microphone input of the intercom and further provides balancing of
an audio level to allow the user's voice to break over the noise gate;
noise reduction ear covers; a volume control switch; and a push-to-talk
(PTT) switch. The vehicle crew communications system, where the wireless
headset includes a rechargeable headset battery, the system further
including a battery charger for charging the rechargeable headset
battery. The vehicle crew communications system, where the base station
includes firmware including an adaptive digital signal processing
algorithm to reduce side tone from the wireless headset.

[0009] A vehicle crew communications system including: a plurality of base
stations where: each base station provides either: five channels each
having: twelve full-duplex TDMA links; a DECT protocol in the 1920-1930
GHz sub-band; an adaptive DSP algorithm incorporated in firmware for
attenuating side tones; and encryption; or ten channels each having:
twelve full-duplex TDMA links; a DECT protocol in the 1880-1900 GHz
sub-band; an adaptive DSP algorithm incorporated in firmware for
attenuating side tones; and encryption; and the plurality of base
stations includes no more than five base stations; an intercom
communicatively coupled to: a base station of the plurality of base
stations via a microphone input in the intercom, where: audio levels from
the intercom to the base station are frequency and gain matched to the
base station; and audio levels from the base station to the intercom are
frequency and gain matched to the intercom ; and a radio. The system also
including four or fewer wireless headsets each wirelessly communicatively
coupled via respective TDMA links to particular respective base stations,
where each wireless headset includes: a head-engaging web; a
noise-cancelling microphone coupled to the web; a microphone circuit
coupled to the microphone; a pair of noise-reduction ear covers coupled
to the web; a volume control switch coupled to one noise-reduction ear
cover of the pair of the noise-reduction ear covers; a push-to-talk (PTT)
switch coupled to one noise-reduction ear cover of the pair of the
noise-reduction ear covers, where the PPT switch is operable to access
the radio; switch the microphone from off to continuously on; and/or
switch the microphone from off to momentarily on; and further including:
either up to sixty wireless headsets of the wireless headset usable at
once with one base station or up to one hundred twenty wireless headsets
of the wireless headset usable at once with one base station; and a range
that is either up to sixteen hundred feet over which the wireless headset
is operable; or up to twenty eight hundred feet over which the wireless
headset is operable, respectively; full duplex communication over
digitally encrypted DECT protocol links from each base station; pairing
of each particular wireless headset to a particular base station of the
plurality of base stations; automatic link and channel selection to avoid
interference, where the selection is transparent to the users; non-manual
selection of a channel for the wireless headset; and a noise-cancelling
microphone with noise threshold, noise attenuation, and line echo
cancellation tuned to parameters of the intercom.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will hereinafter be described in conjunction
with the following drawing figures, wherein like numerals denote like
elements, and

[0011]FIG. 1 is a diagrammatic view illustrating an exemplary vehicle
crew communication system, according to an exemplary embodiment of the
present invention;

[0012]FIG. 2 is a diagrammatic view illustrating the exemplary channel
and slot configuration of the TDMA embodiment of the present invention;
and

[0013]FIG. 3 is an electrical diagram for an intercom that may be used
with the vehicle crew communications system, according to an exemplary
embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The following detailed description of the invention is merely
exemplary in nature and is not intended to limit the invention or the
application and uses of the invention. Furthermore, there is no intention
to be bound by any theory presented in the preceding background of the
invention or the following detailed description of the drawings.

[0015] As used and defined herein, "DECT protocol" is interchangeable with
"DECT 6.0 protocol" and also refers to compatible follow-on versions of
DECT 6.0 protocol.

[0016]FIG. 1 is a diagrammatic view illustrating an exemplary vehicle
crew communication system 100, according to an exemplary embodiment of
the present invention. Vehicle 102 is illustrated as a truck, but the
invention is not so limited. For example, the vehicle may be, without
limitation, a fire engine, an ambulance, or other emergency services
vehicle, a crane, a boat, a mining truck, or an aircraft. The system 100
may be constructed independent of a vehicle 102. In addition, the system
may find some applicability to non-vehicular applications. Wireless
headsets 112, 114, 116, and 118 also represent users of such headsets,
two of whom (112 and 114) are in the vehicle 102 and two of whom (116 and
118) are outside the vehicle 102. A base station 106 coupled to the
vehicle 102 provides full duplex wireless links 120, 122, 124, and 126 to
headsets 118, 116, 114, and 112, respectively.

[0017] Headsets 112, 114, 116, and 118 have a head-engaging web connecting
two noise-reducing ear cups. Headsets 112, 114, 116, and 118 have
push-to-talk (PTT) capability, provided by a button on an ear cup of each
headset 112, 114, 116, or 118, and a microphone with volume control
coupled to the head-engaging web. A preferred headset 112, 114, 116, or
118 has a constantly open headset microphone and uses the PTT switch to
access the radio 130. A less preferred headset 112, 114, 116, or 118 has
no radio 130 access and has an open microphone only when the PTT function
is activated, preferably by depressing a button on an earpiece of the
headset 112, 114, 116, or 118. In another alternate embodiment, for use
where background noise is too high, the microphone may be activated by a
PTT button. Each headset 112, 114, 116, and 118 has a noise cancelling
microphone, noise reduction ear covers coupled to the web, and a volume
control switch. The noise reduction ear covers include the ear cups,
sound-damping foam inside the ear cup, and ear seals around the
perimeters of the ear cups. The headset 112, 114, 116, or 118 may be
designed variously for use under a helmet or hardhat or for use without a
helmet. In an alternate embodiment, wireless links 120, 122, 124, and 126
may be half-duplex, using an alternate protocol and wireless platform.

[0018] The number of headsets 112, 114, 116, and 118 shown is not intended
to limit the invention to four headsets 112, 114, 116, and 118, as will
be further discussed below. Headsets 112, 114, 116, and 118 incorporate a
noise-canceling microphone with a bidirectional (sometimes
hyper-cardioid) pattern that cancel the far field sounds and amplify the
near field sounds. Noise canceling microphones work better for low
frequency noise rather than high frequency noise. In addition, the
microphone circuits of headsets 112, 114, 116, and 118 employ noise
gating. Noise gating means that a threshold is set for the microphone
input level, below which everything is treated as noise and therefore is
not passed through. Any sound has to be loud enough at near field from
the microphone in order to get over the noise gate threshold. To be
successful, noise gating requires setting the noise threshold and
attenuation level in the headsets 112, 114, 116, and 118 to interact
correctly with the respective noise gate parameters on the intercom's 110
microphone input. Another critical feature is the balancing of the audio
level for the artificial side tone in order to create the correct
psycho-acoustic feedback for the user in order to enable him to break
over the noise gate consistently. Unbalanced noise-gating results in
clipping off the first syllable(s) of words or having background noise
overwhelm the conversation.

[0019] Inherent in the nature of the DECT 6.0 protocol is a significant
delay associated with voice data processing. This delay is approximately
20 ms (10 ms one way) for a signal transmitted from the headset 112, 114,
116, or 118 to the base station 106 and into the intercom 110, looped
through the intercom 110 and transmitted back by the base station 106 to
the headset 112, 114, 116, or 118. This delay renders the true side tone
(the side tone coming back from the intercom 110) on the headset 112,
114, 116, or 118 extremely echo ridden which causes a significant amount
of user dissatisfaction during use. An adaptive DSP algorithm
incorporated in the base station firmware called the LEC (Line Echo
Canceller), with proper tuning and application-specific parameterization
is preferred for reducing line echo. This is a rather sophisticated
routine with many parameters that must be tuned just right in order to
operate optimally. The function of the LEC is to eliminate (or severely
attenuate) a particular wireless headset's side tone coming back from the
intercom while preserving the audio coming from other wireless bases
stations 105 and wired headsets 112, 114, 116, and 118 connected to other
slots on the intercom. This means that the parameters of the LEC as well
as the audio levels coming out and going into the base station have to be
adjusted just right to match the frequency response and gain (transfer
function) of the intercom 110 system in order to achieve a satisfactory
echo suppression performance. At the point when the real side tone of the
headset (in this case treated as echo by the base station) is eliminated,
the artificial side tone on the headset is then enabled.

[0020] Base station 106 is coupled into intercom 110, which manages
communications switching. Preferably, more than one base station 106 may
be coupled to one intercom 110. For example, up to six base stations may
be coupled to a Firecom® 3020R intercom 110 manufactured by Sonetics
Corporation of Portland, Oreg. In the present embodiment, each base
station has five channels and up to five headsets may be "paired" to each
base station. Preferably, no more than four headsets 112, 114, 116, and
118 are in use with one five-channel base station 106 at any given time.
Multiple base stations 106 may be used with each intercom 110, allowing
for a large number of headsets 112, 114, 116, and 118 per vehicle 102.

[0021] Optionally, at least one radio 130, for long-distance communication
outside the vehicle 102, may be coupled to the intercom 110 to provide
all users access to information arriving over the radio. For example, up
to two radios 130 may be coupled to a Firecom® 3020R intercom 110. Any
user of headset 112, 114, 116, or 118 may communicate over radio 130 and
one user may be assigned a priority radio transmission slot on the
intercom 110 allowing priority transmission over the radio 130. In an
alternate embodiment, the preferred slot for radio communication may be
switchable. For example, while a fire truck is heading to a fire, the
driver may be connected to radio 130. Once at the fire, the ranking
fireman may be switched into the radio 130. When two radios 130 are
coupled to intercom 110, a faceplate switch enables switching between
radios. In an alternate embodiment, the radios 130 may be switched
remotely via a switch on a headset 112, 114, 116, or 118.

[0022] Base station 106 is preferably attached to the vehicle in a high
position that avoids proximity to metal in order to minimize interference
between metal in the vehicle 102 and the wireless signals going to and
from the base station 106. In a preferred embodiment, the vehicle 102 is
designed to accommodate the base station 106 in a position where
interference (including antenna pattern skew and RF attenuation) from
metal surfaces and objects that are part of the vehicle 102 is minimal.
For example, base station may be located high up on a front window of the
vehicle 102. In another preferred embodiment, the base station 106 may be
integral to (built into) the vehicle 102 in an advantageous position. In
another embodiment, the vehicle 102 body may be made of a material that
is at least partially transparent at the operating frequencies of the
base station 106 and headsets 112, 114, 116, and 118. As an exemplary
embodiment, the vehicle may have a vertical boom extending from a
non-metallic vehicle 102 roof, (i.e. fiberglass), to maximize wireless
coverage.

[0023] In a preferred embodiment, the vehicle 102 will have charging
stations 136 for the wireless headsets 112, 114, 116, and 118, which is
preferably by wires leading from the charger 136 to be plugged in to the
headsets 112, 114, 116, and 118. Placement of charger 136 in FIG. 1 is
not intended to be limiting. The headsets 112, 114, 116, and 118
preferably operate while charging. In an alternate embodiment, a
rechargeable battery station 138 for recharging headset batteries is
integral to the vehicle 102. Placement of battery charger 138 in FIG. 1
is not intended to be limiting.

[0024] Depending on the environment in which the vehicle 102 may be used,
the vehicle 102 and headsets 112, 114, 116, and 118 are preferably made
of materials that can withstand environmental influences such as heat,
cold, rain, sea water spray, and the like. Further, the headsets 112,
114, 116, and 118 preferably comply with occupational safety regulations.

[0025]FIG. 2 is a diagrammatic view illustrating a snapshot of the
exemplary channel 211-215 and slot 221-232 configuration of an exemplary
embodiment of the present invention. The base station 106 preferably
provides five channels 211, 212, 213, 214, and 215 in a DECT 6.0 protocol
Unlicensed Personal Communications Services (UPCS) at 1920-1930 GHz
sub-band. Each channel preferably provides twelve TDMA slots 221, 222,
223, 224, 225, 226, 227, 228, 229, 230, 231, and 232. This theoretically
allows up to sixty headsets per base station 106, although sixty headsets
is usually not operationally preferred. Each headset 112, 114, 116, 118,
are paired to a particular base station 106 and cannot be used with other
base stations 106 without reprogramming. Base station 106 is preferably
coupled to intercom 110 through a connector 204, such as an RJ-12
connector 204. Intercom 110 may have multiple ports 202 (one labeled,
five shown) for coupling in additional base stations 106 with additional
headsets. Intercom 110 may also have a speaker with volume control (not
shown).

[0027] Voice communications over wireless links 120, 122, 124, and 126 are
digital and are encrypted to reduce the risk of interception and
spoofing. The DECT 6.0 protocol detects which slot 221-232 in channels
211-215 has the lowest level of interference based on a preset

[0028] Radio Signal Strength Indication (RSSI) and automatically switches
to that particular slot in that particular channel 211-215. Keeping the
number of headsets in use below sixty supports this capability: if every
channel 211-215 is saturated, there are no available slots to switch to
when interference is to be avoided. The switching between slots 221-232
and channels 211-215 during a given conversation is automatic and
transparent to the user.

[0029] In other frequency bands, more than five channels may be available
and a larger number of headsets may be supported by appropriately
designed base stations 106.

[0030]FIG. 3 is an electrical diagram for an intercom 110 that may be
used with the vehicle crew communications system 100, according to an
exemplary embodiment of the present invention. Headset 118 is wirelessly
linked to multiple headset base station 106 which feeds the microphone
audio through preamp 333 and then into summing amplifier 302. The output
of summing amplifier 302 goes to audio amplifiers 318, 319, and 320. The
output of audio amplifier 320 is coupled to multiple-headset base station
106 and transmitted wirelessly to headset 118 and also to single-headset
base station 310 and transmitted wirelessly to headset 308. Audio
amplifier 319 exemplifies an audio amplifier that supplies other audio
loads (not shown) having impedance different from the base stations 310
and 106. Audio amplifier 318 supplies audio signals to wired headsets 304
and 306. Preamp 330 amplifies the microphone audio from wired headset 304
and feeds the amplified audio to summing amplifier 302. Preamp 331
amplifies the microphone audio from wired headset 306 and feeds the
amplified audio to summing amplifier 302. Preamp 332 amplifies the
microphone audio from single-headset base station 310 which received the
microphone audio from headset 308 and feeds the amplified audio to
summing amplifier 302. A plurality of multiple-headset base stations 106
may be connected with the addition of more audio amplifiers and preamps.

[0031] The features represented in the present invention include up to
sixty headsets 112, 114, 116, and 118, a range of up to 1600 feet for the
headsets 112, 114, 116, and 118, full duplex communication over digitally
encrypted DECT 6.0 protocol links from one base station 106 to a
plurality of headsets 112, 114, 116, and 118, pairing of headsets 112,
114, 116, and 118 with particular base stations 106, the use of only
wireless technology for communications inside and within range of the
vehicle, automatic channel selection to minimally-interfered-with
channels, and removal of the need for manual channel selection in a
wireless headset. Also, the combination of the noise-cancelling
microphone with noise threshold, noise attenuation, and line echo
cancellation tuned to intercom 110 parameters is regarded as novel.
Headsets 112, 114, 116, and 118 that are designed for European use have a
range of up to 2800 feet.

[0032] Although applicant has described applicant's preferred embodiments
of this invention, it will be understood that the broadest scope of this
invention includes alternate embodiments such as those using diverse
types of materials, circuits, and appliances that accomplish the same
purpose in the same way. Such scope is limited only by the below claims
as read in connection with the above specification. Further, many other
advantages of applicant's invention will be apparent to those skilled in
the art who are enlightened by the above descriptions and the below
claims.